Effect of the second filler which melted during composite fabrication on the electrical properties of short fiber polymer-matrix composites.

This paper presents a method for greatly enhancing the electrical conductivity and electromagnetic interference shielding effectiveness of short conducting fiber filled polymers. This method involves the addition of a small proportion of metal particles as a second filler to the fiber polymer-matrix composite. The key to the method is that the metal particles melt during the composite fabrication, so that the metal electrically connects the metal-coated carbon fibers to a certain degree, thereby resulting in a partially connected three-dimensional network. By adding 2 vol% tin-lead particles to 20 vol% short nickel-coated carbon fiber filled polyether sulfone, the electrical resistivity was decreased by a factor of 2000, while the shielding effectiveness at 1 GHz was increased from 19 to 45 dB. No such improvement was found for the same volume fraction of tinlead particles added to an uncoated carbon fiber composite. This difference is due to the superior wetting of solder with nickel compared to that of solder with carbon, as shown by contact angle measurements. [ABSTRACT FROM AUTHOR]